1. Field of the Invention
The present invention relates to the field of image tracking, e.g., tracking an object within an image.
2. State of the Art
Conventional image-based tracking systems, for example those used in infra-red (IR) missile-based tracking systems for guiding missiles, typically use a conventional Fast Fourier Transform (FFT) correlation tracker to track an reference image or object within an image frame. The conventional FFT correlation tracker computes a correlation function between the reference image, saved for example from previous image frames, and the current input image frame. The correlation function is computed using the FFT technique. The advantage of using an FFT technique is higher image processing speeds, particularly when large search areas in the current image frame and large reference windows are used. The conventional FFT correlation tracker performs well when tracking targets against uniform backgrounds, for example when tracking an airplane against blue sky. However, the conventional FFT correlation tracker performs poorly when tracking targets against non-uniform backgrounds, for example when tracking ground vehicles against a background of rugged terrain.
Accordingly, an urgent need exists for a tracking system that is robust, accurate and effective when tracking targets against non-uniform backgrounds. Such situations commonly arise, for example, in standard-profile combat missions flown by Apache and Comanche helicopters.